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Comment by hetspookjee | Hacker News Reader

One thing I've noticed when coping with severe heat, and often get laughed at, is to wear a wet t-shirt. It's incredible how instantaneous the relief is. I just take an ordinary cotton shirt, fold it neatly into a small packet and run it under the tap. Press it a few times so the water runs through the folded package and then unfold. Don't wring it as it will stretch the cloth beyond repair, and put it on. Initially it will feel weird and uncomfortable, but once it's on I feel my head getting more relaxed by the instant. You can even take a comfortable jog outside in 35C in the blasting sun for up to 10 minutes. The shirt will be near dry by than and it will get uncomfortable very quickly, but think of the possibilities! On extreme days I just wetten the shirt for 4-5 times a day and put a fan on me. No sweat when facing >35 degrees inside.

I tried it with pants as well but if you do so, don't wetten it above the pockets as the multi-layer will make it damp without much of the adiabatic cooling perks.

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The effectiveness of this technique depends on the humidity being low. If you tried this when it's 80+% humidity it probably wouldn't do much.

Was it in fact that high of humidity in BC during this event? I think it wasn't, right? When I looked at Portland's weather on the day it was really hot there, the humidity was around 20%.

In the interior of BC it’s typically quite dry during the summer. It’s basically high desert at least in the south.

At 49C you need a dewpoint of almost 70 (!!) to get 20% relative humidity. thats nasty -- during the heatwave in portland the dewpoint was between 63-68 most days. Usually its ~55. For context, the dewpoint on the east coast during the storm season usually is between 70-75.

Or when it's over 52 degrees outside, when "wet bulb" temperature (= a thermometer in a wet cloth) goes over 35, which is what they've been having in Pakistan. At that temperature, the evaporative cooling effect of water (like sweat) is no longer enough to manage temperature, and even fully healthy and hydrated people can die from heat exposure.

I mean I watched people in Canada in the news this morning and thought, why are they still outside in the sun even?

Just to elaborate on the "thermometer in a wet cloth" explanation...

If you have water at the wet bulb temperature exposed to ambient air, then evaporation and condensation are in equilibrium. Above the wet bulb temperature, there is more evaporation, transferring heat from the water to ambient air. Below it, there is more condensation, transferring heat from ambient air to the water.

Except at 100% humidity, this is higher than the dew point, which is the temperature where water spontaneously condenses out of the air.

> I mean I watched people in Canada in the news this morning and thought, why are they still outside in the sun even?

"Mad Dogs And Englishmen" by Noël Coward (1932)

  In tropical climes there are certain times of day
  When all the citizens retire
  To take their clothes off and perspire
  It's one of those rules the greatest fools obey
  Because the sun is far too sultry
  And one must avoid its ultry-violet ray

  The natives grieve when the white men leave their huts
  Because they're obviously, definitely nuts!

  Mad dogs and Englishmen go out in the midday sun

https://www.youtube.com/watch?v=HPnJM3zWfUo

https://genius.com/Noel-coward-mad-dogs-and-englishmen-lyric...

This gave me a chuckle

it's funny the note of colonialist superiority at the end of this poem when I live in the tropics and we regularly call burnt as fuck tourists 'cocido como un camaron' which means cooked like a shrimp. then they get to spend the next day moaning in bed while we take their hotel money and hit the beach with proper sun protection early in the morning when there's way fewer tourists getting skin cancer for no good reason other than operating at times they're used to. Haha!

> I mean I watched people in Canada in the news this morning and thought, why are they still outside in the sun even?

Dunno about being in the sun, but if you don’t have AC and the house is at ambient temp you might as well be outside (normally in the shade) as you’ll at least get some air.

If you're outside you also need to content with the affects of the sun shining on you.

If you don't have AC there are things you can do to your home keep the temp low through the day. You essentially trap the cooler evening air and keep the sun out.

Agreed. In the weeks of no electricity after TS Ike I regretted taking my window plywood off. I had waited a few days and during those days the house was reasonably not cool thru the day but comfy. Without the plywood things got stuffy quickly (old original uninsulated windows).

That works great until it doesn't. A lot of Canadians depended on this mechanism instead of air conditioning, especially on the prairies which is semi-desert: high days, low nights and low humidity. But when your nighttime low is 27...

A side thought... it's quite incredible how we in "the west" have managed to make our lives flow with little impact from seasons, weather, and stuff like that. Just in general. Thinking about how people had it 200 years ago... it was so different.

> If you don't have AC there are things you can do to your home keep the temp low through the day. You essentially trap the cooler evening air and keep the sun out.

That's the normal way to do it, but it doesn't work when there's no wind and air temp doesn't cool down significantly at night. Even fans throughout the dwelling don't end up cooling that much overall, because they really only move the air that's in their path (unless you already have ceiling fans to create larger turbulences and better mix the air).

> Dunno about being in the sun, but if you dom’t have AC and the house is at ambient temp

Depending on design, houses can be above ambient outdoor temperature without AC

Now is there a way to do architecture to passively remove moisture from the air...?

Yes, dozens of ways to do this honed over millennia in hot humid climates, but put in use only by the fringe minority off grid types in modern societies now. God how I yearn to be a fringe minority off grid type. My time will come.

It often makes me wonder why weather reports dont mention the wet bulb temperatures, is it that these measurements are not usually available from monitoring stations?

Don't most weather reports mention the "feels like" temperature, which is essentially the same thing (temperature adjusted for humidity)?

The NWS has a map with experimental wet bulb data here: https://digital.mdl.nws.noaa.gov/

80% humidity with 35C+ heat means death within 15 minutes.

this is so common in coastal places in Southern India. no death in 15mins here.

I read stuff like this on HN and think that many of you must be living in a different physical reality.

I live in Greece where currently we're in the middle of a heatwave (temperatures above 38C for more than a week). I don't recall a single time in my life where we had high temperatures and high humidity levels. But I've read once that if the temperature is higher than 35C and the humidity above 60% you can't live outside because the body can't expel heat fast enough.

> But I've read once

It's best not to assume what you read on the internet is always true. Some people post things that turn out to be utter nonsense. Easily checkable nonsense to boot.

It's explained further down in the comments. It's the so called wet bulb temperature. I was wrong about the 15 minutes limit though, turns out it's about two hours.

You'll be shocked to learn about steam rooms.

I believe that steam rooms are incompatible with human life in the sense that you will overheat and eventually in a hot steam room. Most people are sensible and exit before this happens.

And, like, the entire American south

In fairness it was air conditioning that turned Florida into useless swamp to tourist paradise/trap.

I really hate it because I know it will only make things worse long term but my North European country is rapidly installing AC everywhere now thanks to increasing heatwaves.

A great positive feedback loop, no? Anthropogenic Climate Change (ACC) creates a need for more AC which in turn creates more ACC which furthers the need for more AC. Yeah I don't see this going well for the next few decades.

I've been in steam rooms. You're strongly advised to stay no longer than twenty minutes inside.

Here's the science behind this claim: https://advances.sciencemag.org/content/6/19/eaaw1838

> While some heat-humidity impacts can be avoided through acclimation and behavioral adaptation (12), there exists an upper limit for survivability under sustained exposure, even with idealized conditions of perfect health, total inactivity, full shade, absence of clothing, and unlimited drinking water (9, 10). A normal internal human body temperature of 36.8° ± 0.5°C requires skin temperatures of around 35°C to maintain a gradient directing heat outward from the core (10, 13). Once the air (dry-bulb) temperature (T) rises above this threshold, metabolic heat can only be shed via sweat-based latent cooling, and at TW exceeding about 35°C, this cooling mechanism loses its effectiveness altogether. Because the ideal physiological and behavioral assumptions are almost never met, severe mortality and morbidity impacts typically occur at much lower values—for example, regions affected by the deadly 2003 European and 2010 Russian heat waves experienced TW values no greater than 28°C (fig. S1). In the literature to date, there have been no observational reports of TW exceeding 35°C and few reports exceeding 33°C (9, 11, 14, 15). The awareness of a physiological limit has prompted modeling studies to ask how soon it may be crossed. Results suggest that, under the business-as-usual RCP8.5 emissions scenario, TW could regularly exceed 35°C in parts of South Asia and the Middle East by the third quarter of the 21st century (14–16).

It is when people who don't have any real understanding of physics or biology make absurd comments.

Reminds me of the comment that a 40 MPH car crash isn't potentially deadly: https://news.ycombinator.com/item?id=26470848

Why? 15 min is a bit of an artistic stretch, but otherwise the statement above is correct. 35C at 80% humidity means wet bulb temperature of 32 degrees, which is not survivable by most humans. 38C at 80% humidity means TW of 35 degrees, which is not survivable by anyone.

I totally agree that's correct except for key qualifying statement.

Do you have a source on this please?

It's the wet bulb thermometer reading (temperature read by a thermometer covered in water-soaked cloth over which air is passed). At 35°C it is considered lethal for humans after a couple of hours.

> Wet bulb thermometer readings are significantly lower than the more familiar dry bulb readings, which do not take humidity into account. Researchers say that at a wet bulb reading of 35C, the body can no longer cool itself by sweating and such a temperature can be fatal in a few hours, even to the fittest people.

https://www.telegraph.co.uk/global-health/climate-and-people...

They're confusing it with a 35 C wet bulb temperature. 35 C dry bulb temperature would only equal 35 C wet bulb temperature at 100% RH.

You can convert with a psychrometric chart [1] or with a calculator [2]. At sea level, 35 C dry bulb, 80% humidity is about 32 C wet bulb. Dangerously hot, yes, but it won't kill you in 15 minutes.

[1] https://upload.wikimedia.org/wikipedia/commons/9/9d/Psychrom...

[2] https://www.omnicalculator.com/physics/wet-bulb

95F at 80% humidity is typical summer weather in the southeastern US (though it's been much cooler this year). Is it comfortable? No, but it's also not death in 15 minutes.

Where does it get 95° F and 80% humidity in the southeastern US? I grew up in Miami, and it was rare to have a day above 90° F in the summer, but the humidity made it unbearable.

I can’t even imagine how hot it would have felt at 95° F or higher with the same humidity—I wouldn’t be surprised if it was deadly.

Houston.

Just as the OP said, these temperatures are deadly.

From https://www.houstontx.gov/health/Epidemiology/e-heat-illness....:

> In the summer of 2000, 26 deaths involving Houston residents were reported. In 2001, 13 deaths were due to heat.

From https://environmenttexas.org/news/txe/global-warming-increas...:

> Thursday, September 6, 2007, HOUSTON – The death toll from extreme heat in Houston each summer will increase from about 24 to nearly 32, resulting in 192 additional heat-related deaths by mid-century

> Just as the OP said, these temperatures are deadly.

> > Thursday, September 6, 2007, HOUSTON – The death toll from extreme heat in Houston each summer will increase from about 24 to nearly 32

The actual number of heat deaths in Houston and Harris County in 2018 was 15; Houston itself sees 4–6 per year. Maybe air conditioning is more common a decade later than was originally predicted, or perhaps medical intervention arrives more quickly or is more effective.

Sources: https://nihhis.cpo.noaa.gov/Urban-Heat-Island-Mapping/Campai... and https://www.houstonpublicmedia.org/articles/news/in-depth/20...

I think the problem with the OP is they said it 'means death'. Can be deadly would be better phrasing, particularly to those who are susceptible.

The reason why I think this distinction is important is because there is some level of heat + humidity where it really does mean death to anyone in some short amount of time.

Which part? I think it gets grosser near the Redlands since you get the mugginess of the glades + less cooling from the ocean. Late July through early August can stabilize around 95, maybe 20% of the days were like that when I lived in Homestead, FL. The other days around that time like 85-92 F w/ 80% humidity.

But I guess you're right -- I've had friends heat stroke after 2-3 hrs of unshaded exposure when it hits ~92+ i.e. soccer pickup games. Shade will carry you a long way, even without AC though -- I have extended family in La Guajira that still lives like this.

Ah, yeah, I can totally see that. I grew up in the South Miami / Coral Gables / Coconut Grove areas...divorced parents so I was all over the place. I did always consider Homestead to be a sweltering swamp with desert heat. Going out there in the summer was always a nice way to get dripping with sweat. :P

> But I guess you're right -- I've had friends heat stroke after 2-3 hrs of unshaded exposure when it hits ~92+ i.e. soccer pickup games. Shade will carry you a long way, even without AC though -- I have extended family in La Guajira that still lives like this.

Oof...yep, same experience, especially when the sun isn't occluded by clouds. It's gnarly.

Atlanta?

Tampa dude... Tampa... east coast FL is typically nicer in climate compared to Gulf Coast. I grew up Gulf Coast, I live on the east coast now. Sooooooooooooo much nicer.

That's surprising to me! I always thought Tampa was more temperature than the east coast.

Cities near the coast are usually more moderate. New Orleans is a counter example that I've been to though. But, look at cities like Columbia, SC or Atlanta, GA. Very high humidity and very high day time temps in July and August.

No it doesn’t, that was pretty much the weather in Boston on Monday. It was pretty dreadful being out in it, but not deadly.

Crazy that steam rooms exist then…

Who knew that saunas are actually death chambers...

A sauna has extremely low humidity. A steam room, on the other hand..

Not quite. There are dry saunas. And wet saunas. And everything in between. And then there are steam rooms. They are different things.

Sauna are dry. The wet ones are hammam.

Completely false. Traditional authentic Finnish (where sauna was invented) sauna is wet. Dry sauna is some weird American concoction.

Laughs in slavic banya.

You soft western babies with your dry saunas. Over there the banya is kept at 110% humidity, and old men beat you with sticks the whole time.

This is not in line with the traditional sauna definition.

https://www.imdb.com/title/tt1877543/

They are, but not in 15 mintues - it's more like a few hours. But a human being can't survive for extended periods of time in a sauna.

4 million people in Houston would beg to differ.

I’m sure there are many other places as well.

My family and I were outside in above 35C and 80% humidity for over 8 hours two weeks ago and everyone was fine. Lots of walking etc with no issues.

I can easily stay 15 minutes in a hammam. That is > 40°C and > 95% humidity. I think I have sometimes reached 30 minutes

Then as a Basque I would die on some heat waves in August happening every decade or so.

No it does not. You wet your shirt with unheated tap water, wring it out, and wear it. Repeat as necessary every 15 minutes to 1 hour in extreme heat, no matter how humid it is.

In high humidity by wearing a shirt doused in tap water you cool down by heating up your t-shirt. This method does not work if water comes out of your tap already hot. This only happens rarely. In dry environments evaporative cooling helps but it is not necessary to be effective.

I recommend using shirts made of elastic breathable material such as under armor shirts for comfort. Cotton tends to stick to your skin extra and feel really nasty.

Elastic breathable material in my experience take less water in, so you have to repeat wettin them more often.

If that is the effect you are going for, would wearing a camelback water bladder have a similar effect? It has slightly less surface area to interface with your body, but you can carry a much larger amount of water.

And put it in the freezer intermittently...

Tap water is colder than the inside of the house. Bringing it into the house reduces the heat inside. Putting it into the freezer heats the room that the freezer is in. You're better off replacing the water when it gets warm. Kinda fucked in a drought, though.

How lasting is this effect though compared to evaporative cooling (which lasts for as long as you stay hydrated due to the replenishment of moisture from sweat)? The volume of liquid you're adding to your garment can't be all that much, and if you combine your body heat with a high ambient temperature it seems like the water should reach equilibrium rather quickly.

I don't doubt it helps in the short term - I live in the southeast and I've done this when hiking many times (once my shirt's already soaked from sweat and I can find a cool stream) - but it only provides a temporary respite.

Here are some numbers: the evaporation enthalpy of water is 2,260 kJ/kg at room temperature. The specific heat of water is 4.2 kJ/(kg*K). So for a given amount of water, the evaporation is "worth" about 500 Kelvin of cooling in terms of energy absorbed.

Luckily Lytton is in a semi-desert area - very dry there.

Even here on the coast of BC where humidity is higher (and temps slightly lower), it's reasonably dry right now. Beach towels we put out to dry in the sun are dry in a few minutes.

Seattle is the same, the humidity is high on paper but it didn’t feel like the same 106 in the south, east, or Midwest. It felt…dry hot…like Arizona.

Not as dry as Spokane, however.

If you're in Florida, you don't even have to use the tap. Just put on a dry t-shirt and stand outside for a short while.

Also works like that in Britain half the time :/

Different mechanism in Britain though.

Works this way in TX too. Better yet, just go grab the mail and you'll be set. :D

I've already done that, the t shirt will have a bad smell, and I'm not sure it's very good for the skin. 10min is not very long. Also, gravity will make the water drip down, and the t shirt will not retain a lot of water. Maybe use a thicker cotton.

It feels good at the beginning because the water is cold, but your body will heat the water and it won't be that good. There are special small tower make of platic fiber that will retain more water.

The best way is to drink a lot of water, to use an small pump atomizer that you can refill.

Wetting your hair as it can retain water is also a good solution.

The smell will come later. I'd recommend washing the shirt after a day to remove the bad smell. The 10 min is in the full sun while exercising. Sitting behind a desk in a closed environment I'm able to wear it for ±1-2 hours with effective cooling. If the shirt is dripping water, it's too wet and you should press out the water more. Also a thicker cotton feels less comfortable in my opinion, I prefer to wear a thin one and wetten it more frequently!

Yeah your T-shirt is basically doing the sweating for you then. It's the same mechanism.

Another tip I’ve seen, if you have heat over 100 you’re not supposed to use a fan. The moving air removes the cooler air slightly above the skin and replaces it with warmer air. Under 100 it’s good to use a fan.

Running water (such as a stream) is going to likely be better as you rarely have 100 degree water, but I’m assuming the same applies.

My reasoning is that the cooling actually comes from adiabatic cooling, so using a fan to speed up the evaporation will improve the cooling effect. Mileage may vary though considering the humidity and temperatures.

I think you mean evaporative, not adiabatic.

I have to deal with this problem living in a room with no AC/central air and I have some tips that may be useful for others in the same situation.

1. Put a frozen water bottle under your shirt. Keep backups in the freezer to cycle from. It seriously feels amazing and sucks the heat out of your body.

2. Use two or more fans, one good one to blow air at yourself and another one that is redirecting hot air away from you (so it's facing somewhere away from you). It's just like how airflow in a computer works I guess lol

3. Have ice always available, drink a ton of ice water and stay hydrated.

The difference between doing these things and not doing these things for me is having a somewhat productive day vs spending the whole day doing nothing.

At 49.6C air must be as dry as possible and people likely need a source of colder water as well in order to have a chance of survival because that's obviously extremely hot (body must somehow be able to be 12-13 cooler than air!)

See [1]

[1] https://www.carbonbrief.org/billions-face-deadly-threshold-h...

You can do this with a wet sock to cool down water bottles in the desert. Maybe that helps someone at burning man one day.

What is the humidity when you try this? I am guessing dry and arid.

That tends to be case in the northwestern US this time of year, so I’m guessing that’s true for BC as well. So, it seems like good advice to me.

I live in the mountains of Central Arizona, and I do something similar. On really hot summer days, I will take a 45 second cold shower ever few hours. Probably not so healthy to shock the body, but it helps with the heat.

About ten years ago we installed solar panels so now air conditioning is basically free during the day, but I still like the ice cold showers.

Similarly, run your head under cold water

I find that drinking near-freezing-temperature water also helps, although it's somewhat limited by your stomach's ability to transfer heat. I think the cold constricts blood vessels in the stomach and limits the total amount of heat-transfer-per-second pretty quickly, resulting in a "water baby" that takes 20-30 minutes to come up to temperature and leave the stomach.

It's great the first couple minutes, though.

Bingo... when I was a kid, we lived south of Miami and were part of a cult (different story for a different time, lol). We spent a lot of the summer time on intersections handing out miscellaneous religious texts to commuters in their cars. In any case, the wet t-shirt concept was too uncomfortable and chaffed.

Instead, we ended up taking our baseball caps, dipping them in freezing cold water coolers, and putting them on our head. You'd get like, 20 minutes of relief before returning to dunk the hat again. Having the soaking hat drip on your face and neck provides a similar experience to running your head under cold water without needing an accessible spigot.

That actually sounds like a better idea than me dousing myself during a run. But then again, I wouldn't jog in this heat. My cap for outside running is about 95*F here in the midwest. If anyone wanted to know my cold temp it's about -25*F including wind chill.

This works extremely well on a motorcycle at any speed above 20 km/h, even under protective gear (the only way I've tested). So well that I actually feel a bit cold at first when it's hot but not extreme (below 30°C).

You can also buy ice packs that you wear draped around your neck. It cools the blood flowing to your cartoid artery, along with the general area. Works really well.

Exact. And a similar trick can be used with a bed sheet hanging extended in rope for cooling your bedroom in very hot nights.

You can find cheap (~$5) neck wraps made of PVA fabric that do really well at this evaporative cooling effect.

You can also sleep under a wet towel.

Why not wet a kiffeya or a scarf and wrap it around your neck? Cools you faster

You could do both =). Make all your clothes wet and let adiabatic cooling do it's work for you

If I jogged for ten minutes in 35c my shirt would be wetter than it was when I pulled it out of the sink.

No sweat when facing >35 degrees inside. Why in the world would you have to deal with >35c inside? Do you do construction? Frequent power failures?

I love that you simply cannot imagine that houses without air conditioning could exist. In a thread about the weather in Canada, even.

Having no AC because it rarely gets hot is like having no roof on your house because it never rains. It's a silly risk to take, especially when heat pump systems cool and heat the house equally well and much more efficiently than furnaces or resistive heaters.

I live in a developed country where, I estimate, less than 1% of houses have AC.

35°C inside can totally happen in a house or an apartment without AC and window shutters.

Not sure about BC, buy here in Quebec, not everyone has AC. I mean, it's not that uncommon, but off the top of my head I'd head estimate that roughly a third of people have AC?

Of course, when a heat wave comes, everyone wants to buy one of those windows or floor units, but then they sell out at every store in a few days.

I don't have AC in our house, but we do ga e a basement that stays cool even in extreme heat. Not that fun living in a basement, but realistically the AC would only get used a few days a year in average.

The answer to climate change is to wet a t-shirt and sit next to a fan in your damp armchair while watching the world burn. Talk about frog in a pot.

At least it's something that can be done.

Why equate a clever tactic for instant relief for an individual stuck in a potentially fatal heat wave with "the answer to climate change"? Does the inexorable rise in atmospheric CO2 somehow make it unacceptable for a person to seek relief from heat?

It was really a flippant comment on the state of the world today. I think it's still relevant. We are dealing with the affects very well, but not the cause. This is typical of how humans function and worth pointing out if only for gallows/morbid humour.

According to Lancet, extreme cold kills 20x more people than extreme heat every year. As summers get hotter and winters become milder, fewer humans will die on account of extreme temperatures.

Got a link to the source for that ratio? Also, your conclusion definitely doesn't follow from that ratio alone. A simple example:

Before: cold kills 20 people, heat kills 1 person. Cold kills 20x more, for a total of 21 deaths.

After: cold kills 15 people, heat kills 15 people. Cold kills the same number of people as heat, for a total of 30 deaths.

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

Thanks!

"However, if—as the data seem to show—extreme cold is relatively unimportant, then a few degrees of warming will not yield a large reduction in cold-related mortality. Moreover, if extreme heat is important, then the same few additional degrees might cause a substantial increase in heat-related mortality."

The study warns that global warming won't appreciably reduce deaths due to cold, but might substantially increase deaths due to heat. Again, the current 20-fold factor between deaths due to cold and heat says nothing about future mortality.

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